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Fat free recipe

Drainage - Sewer maintenance

Congealed fat in sewers causes massive blockage problems. A novel invention has opened a new front in the fight against fat, as Diarmaid Fleming explains.

Without a grapefruit or bowl of lentil soup in sight, engineers are making spectacular headway in the bid to become fat-free. The fight against fat is not being fought in the glamorous surrounds of health farms or £1,000 a year gyms. Instead the battleground is in the stygian reaches of the sewers under our streets.

And for water companies it is a battle worth winning. Annually, hundreds of thousands of blockages occur across the country due to build ups of fat poured down the sinks of houses and businesses.

'Keeping sewers open is a major problem - we at Thames Water alone get around 100,000 blockages a year, ' says area operations manager John Kingdon. Around half of these are formed by fat. 'Clearing them is expensive and time consuming - it can be anything from having to get a 'man with a van' to needing to send a crew with a jetting machine. The cost to us is around £6M a year, ' he says.

In once case, a severe build-up of fat in central London's Leicester Square led to the formation of a 50m long block of fat. Clearing it required a team to enter the Victorian sewer with pickaxes.

Pouring fat down the drain is against the law, but enforcing this is almost impossible. Fat from households is not the main cause of difficulties - the major culprits are restaurants and food businesses.

'Fat and grease traps should be in every restaurant, and emptied regularly but people don't tend to do that. If we suspect a business is a source of fat, we can send a letter but there is nothing they have to do legally because we don't have the statutory power of enforcement as environmental health officials do, ' says Kingdon.

So it would appear the graft against grease remains an exercise in grim crisis management: allow enough fat to build up in the drains to form a blockage whose arrival is unpleasantly heralded above ground before taking any action.

But this could all change. A new weapon has been developed in the sewer war against fat - one which aims to destroy the fat before it can build up.

The 'Fatbuster' system is effectively a small intelligent pump which feeds a battalion of specially bred bacteria whose favourite activity is to attack fat.

Once broken down, the fat dissolves away, eliminating the risk of blockage-causing build-ups.

'The pump is peristaltic, working in the same way as your stomach. It releases a dose of bacteria. These are class one - completely safe - naturally occurring micro-organisms, but are super-bred, in the same way as thoroughbred racehorses or prize cattle, to deal with fat.

When it comes to fat fighting, these are the SAS of bacteria, ' says manufacturer Metorod manager André Hopkins.

The pumps, which are about 75mm wide, 50mm deep, and 200mm long, have an on-board computer which regulates the flow and dose of bacteria. 'We generally try to install the pumps where pollution is entering a line, and pre-programme the dosage, ' says Hopkins.

Once unleashed, the bacteria set to work. Combined, 'they create a biofilm - a layer - and start to analyse all the organic material they encounter. They produce millions of enzymes to break down the material. When the bacteria encounter fat and grease, these are broken down and digested. This process puts fat and grease into permanent suspension which just flows away, ' says Hopkins. The bacteria also enjoy their jobs so much that, the more fat they are fed, the more they thrive.

Kingdon says the invention is being piloted in locations around Windsor where, with a heavy concentration of restaurants, major blockages are a recurring problem. Meanwhile, Hopkins says a number of major restaurant and fast-food chains are using the system in other parts of the country.

Slowly but steadily fat is being outflanked: The war against fat may be entering its final phase.

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